TECHNICAL FIELD

This relates to inverters used in electrical vehicles and specifically to means and arrangements to seal electrical connectors or terminals (such as pins and bus bars) thereof, to prevent ingress of fluids and/or particles to the inverter.

BACKGROUND OF THE INVENTION An inverter is a device that converts DC power to the AC power used in an electric vehicle motor. The inverter can change the speed at which the motor rotates by adjusting the frequency of the alternating current. It can also increase or decrease the power or torque of the motor by adjusting the amplitude of the signal.

Typically, the inverter has electrical terminals in the form of bus bars or pins which protrude from the inverter for suitable connection to components external of the inverter.

It is critical that there is no flow of any fluid into the inverter such as oil, fuel or water. Hence there is a need for the terminals to be formed with a fluid-tight connection; i.e. a sealed connection. . The current state of the art to avoid any contamination or extra liquid flowing into the inverter through the connector (to avoid damage to the inverter and potentially lose control of the vehicle) is to use a dispense/sealing material to seal the pin or the bus bar. The dispense material is expensive because basic silicone cannot be used and flourosilicone is required which is more expensive, Furthermore the process of using such dispense material in fabrication is that it is a long process as curing time is required. It is also difficult to control the quality of the sealant/dispense material filling and the adhesion of the plastic/busbar to get a it good enough for the vehicle life. Also at the end of the assembly line a leak test is also required to evaluate the leak level and if the part fail it is not possible to reuse the parts. There is a customer requirement that there is no leak path from the outside so as not to damage the inverter (short circuit by the particles/performance reduced by machine oil). As mentioned basic silicone is not allowed to not damage the e- machine but fluorosilicone is allowed, so, the current design uses a standard process to seal as “dispense materials” to avoid leaks going between the plastic and the busbar into the inverter.

As mentioned, the two types of dispense materials are used for cost and function point of view are basic silicone and fluor silicone SIFEL2614 (expensive l$/gram). There is a leak issue due to the non-adhesion of the dispense material to the plastic, busbar and to the other dispense material (high rejects/scraps). Several inverters were damaged during testing. SUMMARY OF THE INVENTION

In one aspect is provided a vehicle inverter terminal sealing arrangement comprising a electrical terminal of said inverter sealed into an inverter and having a distal portion of said terminal protruding external to said inverter, wherein said terminal is sealed into said inverter by means of a resilient peripheral seal, said peripheral seal surrounding a portion said terminal, and said seal being wedged between said terminal and at least one portion of said inverter.

Said at least one portion of said inverter may include a cut-away portion or slot through which the terminal protrudes externally, said seal being wedged between said terminal and the periphery of said cut away portion.

Said portion of the inverter may be the inverter housing. Said portion of the inverter may be a ferrite core housing or housing component.

Said terminal may be a bus bar or pin of substantially rectangular cross section. Said peripheral seal may be elongate.

Said seal may comprises a peripheral wall and such that varying thickness of the wall varies or the wall has a portion which is conical/tapered cross section.

Said seal may be wedged between said terminal and a first component of said invertor and also between said terminal and a second component of said invertor.

Said seal may be wedged between first component and second component of said invertor.

Said seal may be wedged between upper and lower ferrite core housings.

The portion of the upper ferrite core housing where the seal is wedged, may be the (bottom) surface of a central portion of the upper ferrite housing.

The seal may be wedged between upper ferrite core housing and portion of the inverter housing wall. At least one or both of said first and second invertor components may include a slot portion through which the terminal protrudes, said seal being wedged between said terminal and the periphery of said cut away portion

Any of said slots may include a recess or shoulder to receive or locate said seal wherein said portion of the inverter.

Said recess(es) or shoulder (s) may correspond substantially to the seal peripheral shape The arrangement may include spring means adapted to wedge, retain or place said seal under compression.

Said spring means comprises a spring clip. The arrangement may include means to connect said first invertor component to said second inverter component; said connecting means acting also to compress said seal.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now described by way of example with reference to the accompanying drawings in which:

- Figure la and b shows figures of an electric vehicle inverter showing a prior art sealing arrangement;

Figures 2a to 2e shows an example of an inverter sealing arrangement according to an example of the invention; - Figure 3a and 3 b shows a schematic view of a bus bar seal according to one example.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figure la shows a schematic figure of a cut away portion of a known electric vehicle inverter showing the salient components. The figure shows a prior art sealing arrangement. An (e.g. plastic) housing generally designated 2 may comprise an upper (plastic) housing 12 and a (lower) plastic housing 13, and is located onto the bottom/base portion 7 of the inverter (outer) housing designated with reference numeral 1.

The plastic housings contains a ferrite core 3 so the upper and lower plastic housing has the ferrite inside. Terminal pins or bus bars are shown designated with reference numeral 4. These protrude i.e. extend from the internal portion of the inverter i.e. within the inverter housing, through the housing 2 to the exterior of the inverter at the bottom. The external/ terminal ends of the pins/busbars are designated with reference numeral 5. There is a seal/sealing interface 6 between the lower plastic housing and the base 7 i.e. bottom of the inverter housing. The bus bar can be considered as comprising two portions a first (upper) portion 8 and a second (lower) portion 9, the latter which protrudes externally from the inverter and which needs to be sealed. The upper and lower housings 12 and 13 may be provided or considered as a single overmould housing

Figure lb shows the ferrite core 3 in more detail and reference numerals designate the same components as figure la. The portions of the bus bar is embedded into the housing 2 using a first sealing/dispense material 10 (for e.g. the central portion of the bus bar), which may be silicone. A second dispense material 11 of flourosilicon is used to seal the lower (external portion) of the bus bar (4/9) to/within the lower portion of the overmould housing. As mentioned, the use of flourosilicon has problems such that it is expensive. Arrows A in both figures shows the possible leak paths.

Figure 2a shows a schematic view ( a cross sectional view in a cut -away portion of the inverter housing) of one example of the invention. Again, reference numerals designate the same components as in the previous figures. Figure 2b shows a further cross sectional view of the arrangement of figure 2a and figure 2c shows a cross sectional view of the arrangement in the direction of arrow B of figure 2b. Figure 2c shows a plurality of bus bars/terminal pins 4.

Figure 2d shows the exterior of the arrangement. This shows an upper portion 12 of the ferrite housing 2 (fabricated from plastic) and the lower portion 13 thereof which may also be of plastic. The upper portion 12 is connected to the lower portion 13 by e.g. tapping and bolt/screw means 21, which also provides means to affix the arrangement of the overmould housing (including upper and lower portions (12,13 with the core 3)) to the lower wall 7 of the inverter housing. As can be seen in figure 2a the lower wall 30 of the inverter housing has a cut away portion to expose the lower wall of the lower ferrite housing portion. Thus here the distal end of the bus/bar terminal protrude externally directly from the assembly. It should be noted that alternatively the bus bar may protrude externally from the inverter housing. Thus in an example it may be considered that the lower portion 13 of the overmould may be integral with i.e., formed by a portion of the lower wall of the inverter housing 7. In other words, there they may not be a separate lower portion component, and the exterior of the pin/bus bar 5/9 protrudes directly from the inverter wall externally.

A portion of the lower wall of the (lower) ferrite housing and/or the (bottom) wall of the inverter housing, where the seal is located preferably has one or more cut away portions or slots through which the terminal ends 5 of respective bus bars/pins can protrudes to the exterior directly.

Preferably these cut away portions/slots include a slotted recess or other means to provide shoulder which assists in location of the seal.

The lower portion of the ferrite housing, i.e. the lower housing overmoulds the bus bar(s) as is shown in figure 2d. The central portion of the upper portion/housing has reference numeral 14 in figures 2b and 2c.

So in the examples e.g. of figure 2a-d, the first and second dispense material may be dispensed with. A seal 15 which will be explained in more detail hereinafter is shown in the figures 2a to 2e . The seal surround the bus bar at the exposed end i.e. where it protrudes externally from the inverter (e.g. inverter housing /ferrite housing (end 5/9).

The seal in the example is wedged also between the upper and lower ferrite housings. Specifically here e.g. between bottom surface of the central portion of the upper ferrite housing , and the upper surface of the lower ferrite housing 13.

In general the seal which surrounds the bus bar/pin (referred generally as terminal) where the bus bar/pin (terminal) protrudes externally is wedged between the terminal and one or more components of the inverter (assembly). So a slot in the inverter housing may be provided; the terminal protrudes through the slot externally and the seal is wedged between the terminal and the slot periphery.

Alternatively and additionally the seal may be wedged between the terminal (pin/busbar) and two or more inverter components and/or wedged between the two or more invertor components themselves. For example, wedged between the terminal and respective surfaces of the upper and lower ferrite housings and/or the seal may be wedged between respective the upper and lower portions themselves as in figure 2c.

In another example the seal is wedged between the terminal and respective surfaces of the upper ferrite housing and a respective surface of the invertor housing (e.g. lower) wall and/or the seal may be wedged between respective the upper ferrite housing portion and a respective surface of the invertor (e.g. lower) wall. Again here a slot in the lower ferrite housing /inverter housing may be provided where the terminal protrudes through the slot externally and the seal is wedged between the terminal and the slot periphery, as well optionally also as the surface of another inverter component. Again the slots may have recessed regions or other mans to provide a neck or shoulder region to assist locating the seal.

Further a further seal/sealing face or cover 16 may be provided additionally .

Figure 2e shows an expanded (exploded) view of the arrangement of figure 2 a-d. There is provided a compression spring 17 to assist fitting of the core 3. The seal 16 will be compressed during the assembly into the housing by the 3 screws.

Figure 3a and 3 b shows a schematic view of the bus bar seal. The seal is a peripheral seal so formed as to general conform to surround the terminal ( bus bar or pin). As the bus bars in examples may have a flat rectangular cross section, the seal is correspondingly/appropriately formed such that it or the interior thereof is also generally rectangular; i.e. the internal periphery of the seal is also generally rectangular or elongate. The seal may be is formed such the wall 18 of the seal (e.g. external surface) is tapered such that along a portion of the seal wall, the thickness of the seal increases in one direction - e.g. towards the bottom. Thus, the cross section of the seal shown in figure 3b is of a tapered (or at least part tapered) i.e. conical or part-conical form, i.e. cone formed. This allows good fitting of the seal.

The internal surface 19 of the seal/seal wall may have an internal shoulder or shelf

20, which is peripheral and seen in figure 3b as a protrusion. This aids sealing The seal in examples may be located sandwiched between either the upper surface of the bottom portion of the inverter (lower) housing 13 or the upper bottom surface of the lower ferrite housing (in the region of the cut-away(s)) , and the end (face) of the central portion of the upper ferrite housing 14; and surrounds the bus bar.

As the upper ferrite housing 12 may be connected to the lower housing 13 and/or lower surface of the inverter housing by e.g. tapping and bolt/screw means

21, this will provide a degree of compression to ensure deformation of the seal to provide a good sealing (interfaces). The inner bottom face of the inverter lower housing wall (i.e. the inner surface of the housing wall) or the bottom wall of the of the lower overmould may include a recessed/shelf (peripheral) portion to allow fitting of the seal; the recessed portion may correspond to the shape of the seal.

So in examples is provided a busbar seal with preferred appropriate busbar shape design. The seal is designed to seal a rectangular-shape busbar all around and to seal the plastic all around. The seal meets all specifications (temperature, stack-up & pressure). The busbar can be designed with special shape/deburring process to avoid any damaged to the seal during the assembly. The benefits means customer requirements are achieved as there is no leak. The seal price (0.45€ approx./set) is currently cheaper than dispense material (3€ approx. /set). The assembly/arrangement is easy assembly process, shorter assembly cycle time and better-quality control. The term “’’wedged between (component X and Y)” can be considered as the term “located” and also alternatively that the resilient seal is deformed /under compression between X and Y.